A variety of conditions can result in the need for manipulation or treatment of spinal conditions, and many spinal procedures require the use of one or more bone screws. In particular, bone screws can be used in the spine to correct deformities and treat trauma and/or degenerative pathologies. For example, bone screws can be used in instrumentation procedures to affix rods and/or plates to the spine, can be used to immobilize part of the spine to assist fusion by holding bony structures together, and can be used in a variety of other operations to treat spinal conditions. Bone screws can provide a means of anchoring or securing various elements to a spinal segment during these procedures.
In such operations, it is important to accurately insert bone screws at an entry point of choice. It is also important to reduce the tendency of bone screws to turn or skive out of the entry point during the initial insertion attempt. Another desirable attribute would be reducing the number of instruments needed to prepare the boney anatomy for insertion. Initial screw insertion can be a significant challenge, adding difficulty and danger to an operation while possibly requiring additional equipment to prepare an entry point for correct screw placement. One approach to reduce the need for additional equipment is to create a flute, or a vertical cut or groove, in the thread of the screw. This flute feature forms a vertical edge to cut bone as the screw is rotated into bone. However, this approach results in reduced fixation within the boney anatomy once the screw is completely inserted. This reduced fixation potential is amplified with shorter screws.
Accordingly, there remains a need for bone screws having an improved structure for initial screw insertion that reduces the need for additional instruments to prepare an entry point and does not sacrifice potential screw fixation, especially in shorter screw lengths.